1. Field of the Invention
The present invention relates to respiratory masks, or more particularly to modular respiratory masks that offer protection from hazardous chemical and/or biological warfare agents and the like.
2. Description of the Related Art
Protective masks are currently used by the military for protection against chemical and biological contaminants. However, such masks often impose a substantial physiological burden on the wearer. These masks are typically difficult to wear for prolonged periods because they are relatively bulky and heavy, have high breathing resistance, impair vision and communications, cause thermal stress, physical discomfort, and degrade job performance. Furthermore, the demands placed on such protective masks for use by the crews of military vehicles, such as land and sea vehicles and aircraft, are even greater due to the limitations on the size or bulk of such masks in crowded crew cabins, the need to avoid fogging of the lenses, and crew person exhaustion from heat buildup, physical discomfort, and respiratory effort.
Thus, mask systems used by military crews, and particularly vehicle crews, must be optimized for minimal bulk and weight, in order to readily fit within the limited crew space provided. In addition, such masks must be optimized to provide a sufficient flow of purified air for enhancing respiration and comfort, while minimizing lens fogging, heat stress, respiratory effort, and excessive pressure caused by the mask seals on contacted parts of the user's face and head.
Previous efforts to provide crew masks include the U.S. Army M45 (Aircrew) and M42 (Combat Vehicle) masks. These masks use a standard six-point suspension system and an intern periphery design, where the contact point/seal between the mask and the skin of the user is provided by an inwardly turned mask edge. However, the M45 has no powered blower system due to weight and logistic concerns. While the M45 provides adequate unblown protection and defogging properties, this crew mask is known to be somewhat uncomfortable when used in combination with helmet systems, such as aircrew helmets, due to the harness buckles and the presence of the intern seal in the forehead area, where a crew helmet can press the seal into the forehead. In addition, the lack of a powered blower system results in high breathing resistance, adding to crew fatigue.
In an alternative approach, the U.S. Air Force AERP mask system eliminates the face seal, in favor of a neck seal design. In addition, both the U.S. Army M48/M49 and the U.S. Air Force AERP use a dual canister blower system for providing the overpressure needed for protection against inward diffusion of toxic agents, and to provide additional airflow for keeping the lenses free of moisture or fog. Existing blowers are built to provide for air flow rates of approximately 4 cubic feet per minute (CFM) and attendant overpressure. Given the need for an air flow of approximately 4 CFM, the presently employed blowers for all current crew mask systems are sub-optimal in size and bulk.
Thus, there remains a need in the art for a crew mask for protection against chemical or biological toxic agents that provides a comfortable face seal and helmet interface and an optimized size and bulk of the equipment, while still providing adequate protection and defogging.
The present invention provides a solution to this problem. The invention includes a modular helmet-mask assembly which includes a helmet, a face protection assembly, and a transparent, impact resistant lens. The helmet is made of an impact resistant material for protecting the user's head. The face protection assembly, which can be attached and detached from the helmet, includes a face protection shell which is also made of an impact resistant material, for protecting the head and face of the user. The shell includes a vision port through the shell at the level of the eyes of a user, through which a transparent lens can be positioned for protection of the user's eyes. The face protection assembly includes a flexible nosecup assembly within the shell and flexible face seal on an inner surface of the shell. The flexible nosecup assembly is positioned to engage the mouth and nose of the user, and it includes a breathe-through airflow assembly and filter unit. The flexible face seal is disposed on an inner surface of the shell around the nosecup assembly and the lens, such that the face seal engages the face of the user. A strap or harness is attached to the shell or face seal, for adjustably securing the face seal and nosecup to the user's face to maximize comfort and protection while preventing fogging of the lens.